It could not be determined why the glider entered a spin, nor could it be determined why recovery was not successful. Since it was considered highly unlikely that the pilots would intentionally spin the glider at such a low altitude, the spin was almost certainly entered into inadvertently. Before entering the circuit in preparation for landing, the pilots may have encountered a thermal and attempted to gain altitude, perhaps inadvertently allowing the speed to decrease to the point of stall and spin. There was no indication that incapacitation or physiological factors affected the performance of either pilot. Since the glider was still in a spin at ground impact and the investigation revealed no flight control discrepancies before impact, it is likely that the pilots did not execute the proper spin-recovery technique. The possibility that a loose article in the cockpit became jammed in the controls and prevented the pilots from applying proper spin-recovery controls cannot be ruled out. However, it is considered more likely that the very steep, nose-down attitude of the glider while in the spin, coupled with the ground proximity, resulted in the pilot flying retaining pro spin elevator controls. As highlighted in the British Gliding Association report, the retention of aft stick could be expected to be the involuntary reaction of the pilot in such a situation.Analysis It could not be determined why the glider entered a spin, nor could it be determined why recovery was not successful. Since it was considered highly unlikely that the pilots would intentionally spin the glider at such a low altitude, the spin was almost certainly entered into inadvertently. Before entering the circuit in preparation for landing, the pilots may have encountered a thermal and attempted to gain altitude, perhaps inadvertently allowing the speed to decrease to the point of stall and spin. There was no indication that incapacitation or physiological factors affected the performance of either pilot. Since the glider was still in a spin at ground impact and the investigation revealed no flight control discrepancies before impact, it is likely that the pilots did not execute the proper spin-recovery technique. The possibility that a loose article in the cockpit became jammed in the controls and prevented the pilots from applying proper spin-recovery controls cannot be ruled out. However, it is considered more likely that the very steep, nose-down attitude of the glider while in the spin, coupled with the ground proximity, resulted in the pilot flying retaining pro spin elevator controls. As highlighted in the British Gliding Association report, the retention of aft stick could be expected to be the involuntary reaction of the pilot in such a situation. The glider inadvertently entered a spin at approximately 1000feet above ground level and did not recover from the spin before ground impact. The glider pilots likely did not execute the proper spin-recovery technique.Findings as to Causes and Contributing Factors The glider inadvertently entered a spin at approximately 1000feet above ground level and did not recover from the spin before ground impact. The glider pilots likely did not execute the proper spin-recovery technique.